The proposed conference is the 17th in a series of Gordon Research Conferences that originated in 1966 with a conference on cardiac muscle. The major focus of the 1987 conference will be: The molecular basis of the contractile process. The purpose of this conference is to summarize the major areas of progress during the past 3-5 years, and to point the way to those areas which should prove productive for research in the immediate future. The work to be presented will deal with mammalian skeletal, cardiac and smooth muscle as well as with selected non-muscle contractile systems. In the past three years significant progress has been made in a broad range of areas in muscle research. Particular emphasis will be given to new methods involving genetics and molecular biology to discover the relationship between the amino acid sequence of the contractile proteins, their three-dimensional structures and their enzymatic and mechanical activity. A high resolution crystal structure of G-actin may be completed and promises to aid in defining the structure of F-actin filaments. The myosin subfragment-1 head has also been crystalized and progress toward solving the structure of these crystals will be presented. Chemical cross-linking studies, limited proteolysis and new photoaffinity labels have given new insight into the possible domain structure of myosin and to the location of the actin and nucleotide binding sites. New applications of flourescent and spin-labeled probes as well as time-resolved low angle x-ray diffraction are determining cross-bridge orientation in defined mechanical states. The possible regulation of smooth muscle contraction by systems other than light chain phosphorylation will be addressed as will the function of auxiliary and cytoskeletal proteins. A major theme will be the correlation of biochemical information from purified systems with similar studies in skinned muscle fibers. New photolabile precursors of nucleotide analogs allow kinetic experiments in fibers to focus on specific chemical reaction steps. The conference will include a limited number of formal presentations with emphasis being placed on discussion and informal interchanges. Ample use will be made of poster presentations and discussion of this material will be incorporated into the main program. This conference has become a major triennial meeting which attracts the leading investigators in muscle research from around the world. In allowing scientists of diverse backgrounds to focus on the molecular mechanism of muscle contraction for a week, this conference should help to open new areas of research as well as provide a meaningful reexamination of previously accepted ideas.